The Relative Humidity of the Atmosphere in the Encasements Containing the Declaration of Independence, the US Constitution (Pages 1 and 4), and the Bill of Rights

In 1951, the four pages of the US Constitution, the Letter of Transmittal, the Bill of Rights and the Declaration of Independence, collectively called the 'Charters of Freedom,' were hermetically sealed individually in glass encasements. The atmosphere in the encasements consisted of a mixture of helium with water vapor at a relative humidity between 25 and 35% at room temperature. In 1998, Margaret Kelly of the National Archives and Records Administration (NARA), contacted Dr. Joel S. Levine at NASA Langley Research Center (LaRC) to request assistance in determining the chemical composition of the atmosphere inside the encasements. Several different Langley learns were assembled to address that request. each using a different measurement technique. This report describes the method and results of one team's relative humidity measurements on encasements containing pages 1 and 4 of the US Constitution, the Bill of Rights, and the Declaration of Independence performed at NARA, College Park. Maryland, on July 23, 2001.